Providing an external source of power to a mobile device, such as a personal digital assistant (“PDA”), wireless two-way messaging device, cellular phone, etc., requires design considerations with respect to both the mobile device and the power source. Most mobile devices provide a distinct power interface for receiving power from a power source, for instance to recharge a battery, and a separate data interface for communicating. For example, many mobile devices use USB (Universal Serial Bus) interfaces for communicating and use a separate power interface, such as a barrel connector, for receiving power. One reason that a USB interface is not typically used as a power source for a mobile device is that USB specifications require that any devices which are connected to a USB host initiate enumeration within 150 msec of a USB cable being attached. Enumeration is the process whereby devices attached to the USB host request permission to access and draw power from the USB host or hub.